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What is Kaposi sarcoma?

Kaposi sarcoma (KS) is a cancer that develops from the cells that line lymph or blood vessels. It usually appears as tumors on the skin or on mucosal surfaces such as inside the mouth, but tumors can also develop in other parts of the body, such as in the lymph nodes (bean-sized collections of immune cells throughout the body), the lungs, or digestive tract.

The abnormal cells of KS form purple, red, or brown blotches or tumors on the skin. These affected areas are called lesions. The skin lesions of KS most often appear on the legs or face. They may look bad, but they usually cause no symptoms. Some lesions on the legs or in the groin area may cause the legs and feet to swell painfully.

KS can cause serious problems or even become life threatening when the lesions are in the lungs, liver, or digestive tract. KS in the digestive tract, for example, can cause bleeding, while tumors in the lungs may cause trouble breathing.

Types of Kaposi sarcoma

The different types of KS are defined by the different populations it develops in, but the changes within the KS cells are very similar.

Epidemic (AIDS-related) Kaposi sarcoma

The most common type of KS in the United States is epidemic or AIDS-related KS. This type of KS develops in people who are infected with HIV, the virus that causes AIDS.

A person infected with HIV (that is, who is HIV-positive) does not necessarily have AIDS. The virus can be present in the body for a long time, often many years, before causing major illness. The disease known as AIDS begins when the virus has seriously damaged the immune system, which results in certain types of infections or other medical complications, including KS. When HIV damages the immune system, people who also are infected with a certain virus (the Kaposi sarcoma associated herpesvirus or KSHV) are more likely to develop KS.

KS is considered an “AIDS defining” illness. This means that when KS occurs in someone infected with HIV, that person officially has AIDS (and is not just HIV-positive).

In the United States, treating HIV infection with highly active antiretroviral therapy (HAART) has resulted in fewer cases of epidemic KS. Still, some patients develop symptoms of KS in the first few months of HAART treatment.

For most patients with HIV, HAART can often keep advanced KS from developing. Still, KS can still occur in people whose HIV is well controlled with HAART. Once KS develops it is still important to continue HAART.

In areas of the world where HAART is not easy to obtain, KS in AIDS patients can advance quickly.

Classic (Mediterranean) Kaposi sarcoma

Classic KS occurs mainly in older people of Mediterranean, Eastern European, and Middle Eastern heritage. Classic KS is more common in men than in women.

Patients typically have one or more lesions on the legs, ankles, or the soles of the feet. Compared to other types of KS, the lesions in this type do not grow as quickly, and new lesions do not develop as often.

The immune system of people with classic KS is not as weak as it is in those who have epidemic KS, but it may be weaker than normal. Getting older can naturally weaken the immune system a little. When this occurs, people who already have a KSHV (Kaposi sarcoma associated herpesvirus) infection are more likely to develop KS.

Endemic (African) Kaposi sarcoma

Endemic KS occurs in people living in Equatorial Africa and is sometimes called African KS. KSHV (Kaposi sarcoma associated herpesvirus) infection is much more common in Africa than in other parts of the world, so the risk of KS is higher. Other factors in Africa that weaken the immune system (such as malaria, other chronic infections, and malnutrition) also probably contribute to the development of KS, since the disease affects a broader group of people that includes children and women.

Endemic KS tends to occur in younger people (usually under age 40). Rarely a more aggressive form of endemic KS is seen in children before puberty. This type usually affects the lymph nodes and other organs and can progress quickly.

Endemic KS used to be the most common type of KS in Africa. Then, as AIDS became more common in Africa, the epidemic type became more common.

Iatrogenic (transplant-related) Kaposi sarcoma

When KS develops in people whose immune systems have been suppressed after an organ transplant, it is called iatrogenic, or transplant-related KS. Most transplant patients need to take drugs to keep their immune system from rejecting (attacking) the new organ. But by weakening the body’s immune system, these drugs increase the chance that someone infected with KSHV (Kaposi sarcoma associated herpesvirus) will develop KS. Stopping the immune-suppressing drugs or lowering their dose often makes KS lesions go away or get smaller.

Kaposi sarcoma in HIV negative men who have sex with men

There have been reports of KS developing in men who have sex with men who are not infected with HIV. In this group, the cases of KS are often mild, similar to cases of classic KS.